In recent years, an optical image measuring technique of forming an image that shows the surface morphology or internal morphology of a measured object by using a light beam from a laser light source or the like has attracted attention. Unlike an X-ray CT apparatus, the optical image measuring technique is noninvasive to human bodies, and is particularly expected to be utilized more in the medical field and biological field.
Patent Document 1 discloses a device to which the optical image measuring technique is applied. This device has a configuration in which: a measuring arm scans an object by a rotary deflection mirror (a Galvano mirror); a reference arm is provided with a reference mirror; and an interferometer is mounted at the outlet to analyze, by a spectrometer, the intensity of the interference light of light fluxes from the measurement arm and reference arm. Besides, the reference arm is configured to gradually change the light flux phase of the reference light by discontinuous values.
The device of Patent Document 1 uses a technique of so-called “Fourier Domain OCT (Optical Coherence Tomography).” That is to say, the device radiates a low-coherence light beam to a measured object, superpose the reflected light and the reference light on each other to generate the interference light, and acquires the spectral intensity distribution of the interference light to execute Fourier transform, thereby imaging the morphology in the depth direction (z-direction) of a measured object.
Furthermore, the device described in Patent Document 1 is provided with a Galvano mirror that scans with a light beam (a signal light), and is thereby configured to form an image of a desired measurement target region of a measured object. Because this device is configured to scan with the light beam only in one direction (x-direction) orthogonal to the z-direction, an image formed by this device is a two-dimensional tomographic image in the depth direction (z-direction) along the scanning direction (x-direction) of the light beam.
Patent Document 2 discloses a technique of scanning with a signal light in the horizontal direction and the vertical direction to form a plurality of two-dimensional tomographic images in the horizontal direction, and acquiring and imaging three-dimensional tomographic information of a measured range based on the plurality of tomographic images. As the three-dimensional imaging, for example, a method of arranging and displaying the plurality of tomographic images in the vertical direction (referred to as stack data or the like), and a method of executing a rendering process on the plurality of tomographic images to form a three-dimensional image are considered.
Patent Documents 3 and 4 disclose other types of OCT devices.
Patent Document 3 describes an OCT device that images the morphology of a measured object by scanning the measured object with lights of various wavelengths, acquiring the spectral intensity distribution based on the interference light obtained by superposing the reflected lights of the lights of the respective wavelengths on the reference light, and executing Fourier transform thereon. Such an OCT device is called Swept Source type or the like.
Further, Patent Document 4 describes an OCT device that radiates a light having a predetermined beam diameter to a measured object and analyzes the components of the interference light obtained by superposing the reflected light and the reference light on each other, thereby forming an image of the measured object in a cross-section orthogonal to the travelling direction of the light. Such an OCT device is called full-field type, en-face type or the like.
Patent Document 5 discloses a configuration in which the OCT technique is applied to the ophthalmologic field. Before the OCT device was applied to the ophthalmologic field, a fundus oculi observing device such as a retinal camera had been used (for example, refer to Patent Document 6).
A fundus oculi observing device using the OCT technique has a merit that an image of a deep part of the fundus oculi can be obtained, when compared with a retinal camera that images the surface of the fundus oculi. Therefore, contribution to increase of the diagnosis accuracy and early detection of a lesion is expected.    Patent Document 1: Japanese Unexamined Patent Application Publication No. 11-325849    Patent Document 2: Japanese Unexamined Patent Application Publication No. 2002-139421    Patent Document 3: Japanese Unexamined Patent Application Publication No. 2007-24677    Patent Document 4: Japanese Unexamined Patent Application Publication No. 2006-153838    Patent Document 5: Japanese Unexamined Patent Application Publication No. 2008-73099    Patent Document 6: Japanese Unexamined Patent Application Publication No. 9-276232